ENCODER / DECODER: Add functions to encode/decode to/from a buffer

This adds OSSL_ENCODER_to_data() and OSSL_DECODER_from_data().  These
functions allow fairly simple rewrites of type-specific i2d and d2i
calls.

Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/13094)

2 files changed, 32 insertions, 7 deletions

diff --git a/doc/man3/OSSL_DECODER_from_bio.pod b/doc/man3/OSSL_DECODER_from_bio.pod
index 7de550746e..3bd43200d3 100644
--- a/doc/man3/OSSL_DECODER_from_bio.pod
+++ b/doc/man3/OSSL_DECODER_from_bio.pod
@@ -2,6 +2,7 @@
 
 =head1 NAME
 
+OSSL_DECODER_from_data,
 OSSL_DECODER_from_bio,
 OSSL_DECODER_from_fp
 - Routines to perform a decoding
@@ -12,6 +13,8 @@ OSSL_DECODER_from_fp
 
  int OSSL_DECODER_from_bio(OSSL_DECODER_CTX *ctx, BIO *in);
  int OSSL_DECODER_from_fp(OSSL_DECODER_CTX *ctx, FILE *fp);
+ int OSSL_DECODER_from_data(OSSL_DECODER_CTX *ctx, const unsigned char **pdata,
+                            size_t *pdata_len);
 
 Feature availability macros:
 
@@ -24,6 +27,12 @@ is undefined.
 
 =head1 DESCRIPTION
 
+OSSL_DECODER_from_data() runs the decoding process for the context I<ctx>,
+with input coming from I<*pdata>, I<*pdata_len> bytes long.  Both I<*pdata>
+and I<*pdata_len> must be non-NULL.  When OSSL_DECODER_from_data() returns,
+I<*pdata> is updated to point at the location after what has been decoded,
+and I<*pdata_len> to have the number of remaining bytes.
+
 OSSL_DECODER_from_bio() runs the decoding process for the context I<ctx>,
 with the input coming from the B<BIO> I<in>.  Should it make a difference,
 it's recommended to have the BIO set in binary mode rather than text mode.
diff --git a/doc/man3/OSSL_ENCODER_to_bio.pod b/doc/man3/OSSL_ENCODER_to_bio.pod
index 6f75f592e4..f28228bf10 100644
--- a/doc/man3/OSSL_ENCODER_to_bio.pod
+++ b/doc/man3/OSSL_ENCODER_to_bio.pod
@@ -2,6 +2,7 @@
 
 =head1 NAME
 
+OSSL_ENCODER_to_data,
 OSSL_ENCODER_to_bio,
 OSSL_ENCODER_to_fp
 - Routines to perform an encoding
@@ -10,6 +11,8 @@ OSSL_ENCODER_to_fp
 
  #include <openssl/encoder.h>
 
+ int OSSL_ENCODER_to_data(OSSL_ENCODER_CTX *ctx, unsigned char **pdata,
+                          size_t *pdata_len);
  int OSSL_ENCODER_to_bio(OSSL_ENCODER_CTX *ctx, BIO *out);
  int OSSL_ENCODER_to_fp(OSSL_ENCODER_CTX *ctx, FILE *fp);
 
@@ -24,20 +27,33 @@ is undefined.
 
 =head1 DESCRIPTION
 
+OSSL_ENCODER_to_data() runs the encoding process for the context I<ctx>,
+with the output going to the I<*pdata> and I<*pdata_len>.
+If I<*pdata> is NULL when OSSL_ENCODER_to_data() is called, a buffer will be
+allocated using L<OPENSSL_zalloc(3)>, and I<*pdata> will be set to point at
+the start of that buffer, and I<*pdata_len> will be assigned its length when
+OSSL_ENCODER_to_data() returns.
+If I<*pdata> is non-NULL when OSSL_ENCODER_to_data() is called, I<*pdata_len>
+is assumed to have its size.  In this case, I<*pdata> will be set to point
+after the encoded bytes, and I<*pdata_len> will be assigned the number of
+remaining bytes.
+
 OSSL_ENCODER_to_bio() runs the encoding process for the context I<ctx>, with
-the output going to the B<BIO> I<out>.  The application is required to set
-up the B<BIO> properly, for example to have it in text or binary mode if
-that's appropriate.
+the output going to the B<BIO> I<out>.
+
+OSSL_ENCODER_to_fp() does the same thing as OSSL_ENCODER_to_bio(), except
+that the output is going to the B<FILE> I<fp>.
 
 =for comment Know your encoder!
 
-OSSL_ENCODER_to_fp() does the same thing as OSSL_ENCODER_to_bio(),
-except that the output is going to the B<FILE> I<fp>.
+For OSSL_ENCODER_to_bio() and OSSL_ENCODER_to_fp(), the application is
+required to set up the B<BIO> or B<FILE> properly, for example to have
+it in text or binary mode as is appropriate for the encoder output type.
 
 =head1 RETURN VALUES
 
-OSSL_ENCODER_to_bio() and OSSL_ENCODER_to_fp() return 1 on success, or 0 on
-failure.
+OSSL_ENCODER_to_bio(), OSSL_ENCODER_to_fp() and OSSL_ENCODER_to_data()
+return 1 on success, or 0 on failure.
 
 =begin comment TODO(3.0) Add examples!